Control system for an internal combustion engine



l l i ug- 4, 1959 HANS-JoAcHIM M. FRSTER 2,897,809

. CONTROL SYSTEM FOR AN INTERNAL cONBusTIoN ENGINE Filed July s1, 1957 CONTROL SYSTEM FCR AN INTERNAL COMBUSTION ENGINE Hans-:Joachim M. Frster, Smngarcad Cannstatt, Germany, assignor to Daimler-Benz Aktiengesellschaft, Stuttgart-Unterturkheim, Germany My invention relates to a control system for an internal combustion engine of the type in which a fuelair mixture is compressed in each cycle of operation.

It is a requirement for engines of this type that the ratio'by weight of the fuel to the air varies within very narrow limits only. Therefore, the quantity of fuel injected per cycle must be so determined as to be properly correlated to the quantity of air admitted per cycle to the intake pipe of the engine and constituting the filling of the cylinder. In principle two distinct methods of control may be used for compliance with this requirement. In one system the operator in order to control the power produced by the engine adjusts the air quantity, for instance by actuating an accelerator pedal, and automatic control means adjust the fuel quantity in dependence on the air quantity. In the other system the operator in order to control the power produced by the engine adjusts the fuel quantity directly, for instance by actuating an accelerator pedal of a motor vehicle, and suitable control means automatically adjust the air quantity so as to suit the mixture requirements. This latter system has the advantage that, when the driver of a motor vehicle wishing to' accelerate the motor vehicle depresses the accelerator pedal, a richer fuel-air mixture Iwill be temporarily produced until the automatic control means will have increased the air quantity accordingly. This temporary enrichment of the mixture is desirable as the rich mixture will produce a higher power.` resulting in a quick acceleration of the vehicle. As soon as the automatic control means have caught 11p with the increased fuel quantity and have increased the air quantity accordingly, the normal ratio of mixture will be restored. accelerator pedal reducing the fuel quantity a leaner mixture will be produced temporarily, whereby the vehicle will be eiectively retarded.

My invention relates to a control system of the secing in the intake pipe. Owing to such conditions the quantity of air with which the cylinders of the engine are charged may be insuiicient even though the automatic control means have fully opened the throttle valve, when the driver has fully depressed the accelerator pedal causing the maximum fuel quantity to be injected. As a result, the fuel mixture will be richer than desirable with a consequent waste of fuel, jerky operation of the engine, development of smoke in the exhaust, dilution of the lubricant by condensed fuel etc.

Therefore, it is an object of my invention to provide an improved control system of this character in which a movable fuel control member determining the quantity of fuel injected per cycle of operation of the engine will be automatically actuated in a fuel-quantity-reducing direction when the atmospheric pressure is excessively low or the temperature prevailing in the intake pipe is excessively high resulting in insuciency of the quantity of air admitted per cycle to `the intake pipe of the engine.

It is another object of my invention to provide means permitting the'movable fuel control member to be moved in a fuel-quantity-reducing direction even though the operator may keep the brake pedal or other actuating member fully depressed or operated.

Another object of my invention is the provision of an improved control system of the type indicated which is simple and reliable in operation and subject to a minimum of wear so as to ensure longevity. v

Further objects of my invention will appear from a detailed description of a preferred embodiment following hereinafter with reference to the accompanying drawing. It is to be clearly understood, however, that my invention is in no way limited `to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims and that the .terms and phrases used in such detailed description have been chosen for the purpose of illustrating the inventionl rather than that of restricting or limiting same. In the drawing my novel control system is illustrated diagrammatically as applied to the engine of a motor vehicle, some of its elements being shown in section and others in perspective.

A movable fuel control member which, in the embodiment shown, is formed by the accelerator pedal Z of the motor vehicle is connected vby resilient means to Inversely, upon a release of the ond type in 4which an actuating member, such as an accelerator pedal, movable by the operator is connected with the fuel control member, which may be .the control rod of a fuel injection pump, the quantity of air admitted per cycle to the intake pipe of the engine being adjusted by a throttle valve connected to suitable control means ensuring that in the intake pipe the vacuum will be properly correlated to the fuel quantity, such vacuum pressure :being substantially proportional to the weight of the air charge. Since the weight of the air charge also depends on the temperature, the control of the throttle valve is preferably effected in dependence onboth, the vacuum and the temperature prevailing in the intake pipe so as to ensure that the Weight of the air charge admitted to any engine cylinder per cycle of operation .is properly correlated to the quantity of fuel injected.

Prior control systems of this type were unable to cope with problems arising under extraordinary circumstances, such as an extremely low atmospheric pressure prevailing at high altitudes or extremely high temperatures prevailbe described hereinafter with a movable fuel control member formed by pivotally connected rods 3 and 4 adapted to determine the quantity of fuel injected per cycle, the rod 4 constituting the control rod of a conventional fuel injection pump 5. This pump is connected by pipes not shown with the fuel injection nozzles coordinated to the cylinders of the engine and adapted to inject fuel during the suction and/or compression stroke of the pistons. The quantity of fuel injected per cycle into each cylinder is determined by the adjustment of the rod 4. Movement of the rod 4 towards the right will increase the fuel quantity, whereas movement of the rod 4 to the left will reduce the fuel quantity.

Whereas one end of the rod 3 is pivotally connected to the rod 4, its other end is slidably guided in an axial bore in one end of a closed cylindrical casing 6, the other end of which is pivotally connected to a rod 40 which is hinged to the accelerator pedal 2 which is subjected to the force of a spring 1 tending to urge the elements 2, 40, 6, 3, 4 into the uttermost left position in which the fuel quantity injected into each cylinder is reduced to zero. The end of rod 3 projecting into the cylinder 6 carries a disk 7 and a biased helical pressure spring 8 included in the cylindrical casing 6 tends to keep the disk 7 in the position shown so that any movement of the pedal 2 will be transmitted to the fuel con- 3 trol member 3, 4 moving in unison with the elements 2, 40 and 6.

For the purpose of the p resent invention, however, a rev-setting' device Yis co-ordinated to the fuel control member 3, 4 for moving the same in the fuel-quantity-reducing direction* even though the driver may keep the pedal 2 fnlly depressed.

' In the embodiment shown this resetting device is of the Vtype operable by fluid pressure comprising a cylinder 40 fixed to the frame structure of the motor vehicle, a piston 41 slidable in the cylinder 40 and having a piston rod extending through an axial bore in the cover of the cylinder 40 and provided with a knob 44, a helical pressure spring 42 surrounding the piston rod being inserted between the piston 41 and the cover of cylinder 40. The bottom of the cylinder 40 is provided with a port connectedv withv a pipe 39. When uid under pressure is admitted to the pipe 39 it will lift the piston 41 and the knob 44 causing the knob 44 to engage an arm 45 of a shaft V24 extending transversely to the rod 3 beneath the same and journaled yin bearings 41 and 42 fixed to the frame structure of the motor vehicle. The shaft 24 has an upright arm 25 provided with a longitudinal slot 26 straddling a lateral Vpin V27 projecting from the rod 3. Engagement of arm 45 by the knob 44 will turn shaft 24 and arm 25 anti-clockwise, whereby the movable fuel control member 3, 4 will be moved to the left even though the operator may keep the pedal 2 fully depressed holding the cylindrical casing 6 stationary and causing the `spring 8 to be compressed by the disk 7 moving in unison with the rod 3. The intake pipe 9 of the engine is provided with a throttle valve 10 adapted by its adjustment to determine the quantity of air admitted per cycle to the cylinders of the engine. The throttle. valve 10 is adjustable by an actuator which in the embodiment shown is o f the type operable by uid pressure comprising a cylinder 13 fixed to the frame structure of the motor vehicle and a piston 12 movable in the cylinder 13 and having a piston rod extending through an axial bore of the cover of the cylinder 13 and having a transverse pin 43 engaging a slot provided in an arm 44 of a bell crank fulcrumed to a bracket 46 xed to the frame structure of the vehicle. The other arm 45 of the bell crank is connected by a link 11 with an arm of the shaft of the throttle valve 10.

` Moreover, the control system is provided with means responsive to the vacuum prevailing in the intake pipe 9. I n the embodiment shown such means comprises a hollow compressible member 30, preferably a cylindrical 'sheet metal drum having a corrugated wall, and a chamber 29 surrounding the compressible member 30 and communicating with the intake pipe 9 and through a pipe 28. O ne end of the compressible member 30 is fixed to the top wallA of the chamber 29, whereas a rod 31 is fixed to the other end of the compressible member 30 and extends through a bore out of the chamber 29, such bore being provided with sealing rings 47.

The actuator 12, 13 connected with the throttle 10 for the adjustment thereof is controlled jointly by the vacuumfresponsive means 2931 and by the fuel control member 3, 4. For this purpose a control valve iS co-ordinated to the fluid-operable actuator 12, 13 for controlling same. This control valve includes a movable sleeve element 15 provided with ports and a piston element 16 movable in the sleeve element 15 for controlling the ports. The sleeve element 15 constitutes a plunger movable in a cylinder 14 fixed to the frame structure of the motor vehicle. The valve elements 15 and 16 cooperate to control the admission to and the discharge `from the cylinder 13 of a suitable pressure fluid, such as oil, which is admitted through a duct 17 from a suitable source of pressure. This duct is in permanent communication with a peripheral groove 48 of the control piston 16, such permanent communication being established by an, internal annular groove 49 of the cylinder 14 and radial ports 50 of the sleeve element 15. Relative displacement of the two valve elements 15 and 16 will put a pair of ports 51 and 52 of the valve element 15 into alternative communication with the circumferential groove 48 of piston 16 containing oil under pressure or with chambers 53 and 54 disposed` above and below the piston 16 and permanently put on discharge, the chamber 54 being open at its bottom and the chamber 53 being Vented through apertures 55. The port 51 is in permanent communication with an internal annular groove 56 of cylinder 14 connected by a duct 18 with the top chamber of cylinder 13, whereas the port 52 is in permanent comd munication with an internal annular groove 57 of cylinder 14 connected by a duct 19 with the bottom cham ber of the cylinder 13. v

One of the elements 15, 16 is connected with the vacuum-responsive means 29-31 to be adjusted thereby, whereas the other valve member is co-operatively connected with the fuel control member 3, 4 to be adjusted thereby. In the embodiment shown it is the piston element 16 that is connected to the vacuum-responsive means by a two-armed lever 32 having one arm pivotally connected to the end of rod 31 and having its other arm pivotally connected by a link 35 to the piston element 16. The fulcrum of the lever 32 is movably-mounted and means responsive to the temperature prevailing in the intake pipe 9 are connected to the movable fulcrum, whereby the valve element 16 is controlled jointly by the vacuum-responsive means and by the temperature-responsive means. The fulcrum of the lever 32 is formed by a pin 33 carried by the depending larm of a bell crank 37 and engaging a longitudinal slot 34 of the lever 32. The bell crank 37 is carried by a bracket 58 fixed to the frame structure of the motor vehicle. The other arm of the bell crank 37 is connected by a link 59 and a second bell crank 60 and by a link 61 to an arm 62 carried by a bracket 63 mounted on the pipe 9 and held by a tension spring 64 in contact with a thermostat 38 mounted in the intake pipe 9 and responsive to the temperature therein. The bell crank 60 is fulcrumed upon a bracket 65 fixed to the frame structure of the motor vehicle.

When the temperature prevailing in the intake pipe 9 rises, the arm 62 will be turned by the thermostat 38 in anti-clockwise direction moving link 61 to the left and link 59 upwardly, whereby the fulcrum 33 will be moved on an arc of a circle about the fulcrum 36 of bell crank 37 in anti-clockwise direction.

The valve element 15 is co-operatively connected with the fuel control member 3, 4. For this purpose a cam disk 23 is fixed to the shaft 24 and engages an arm 21 mounted for pivotal movement about a stationary but adjustable pin 20 and connected to the valve element 15. A helical pressure spring 22 inserted in the cylinder 14 between the top wall thereof and the sleeve member 15 tends to move the latter downwardly thus keeping the arm 21 in permanent engagement with the cam 23. The connection between the sleeve member 15 and the-arm 21 is constituted by a pin 66 carried by a bracket 67 xed to the lower end of the sleeve member 15 and extending through a suitable slot 68 in the wall of the cylinder 14. The pin 66 engages a slot 69 provided in the end of arm 21.

The adjustable pin 20 is mounted in eccentric position on a rotatable member 70 journaled in a bracket 71 fixed to the frame structure of the vehicle and provided with a handle 72 for manual rotation.

For the purpose of activating the re-setting device 41 to 44 I have provided suitable means controlled by the actuator 12, 13. Such means comprises a port 73 provided in the wall of cylinder 13 and communicating with the pipe 39, the port 73 being so located as to be uncovered by the piston 12, when the actuator 12, 13 after having opened the throttle valve 10, continues its movement in the throttle-valve-.opening direction, that is to sayl in. the

downwarddirection with-reference to the drawing. The piston 12 is provided with suitable valve means controlling the port 73.` In the embodiment shown such valve means comprises a circular disk 74 provided on top of the piston 12 and tightly iitted into the cylinder 13. Beneath the disk 74 there is a clearance 75 Iprovided between the piston 12 and the wall of the cylinder 13, such clearance permanently communicating with aY discharge pipe 76.

When the accelerator pedal 2 is partly depressed to thereby adjust the. fuel injection pump 5 for medium power of the engine, the elements assume the position shown in the drawing. When the driver desirous of increasing the power produced by the engine depresses the pedal 2 starting Ifrom the position shown, the pump control rod 4 is moved towards the right, thereby increasing the Yquantity of fuelV injected. At the same time the arm 25, its shaft i 24 andthe cam 23 are turned in clockwise direction permitting the. spring 22 to depress the valve element 15 and the arm 21 pivotally connected therewith because of the shape of the cam 23 causing the radius of the point of engagement with the arm 21 to be reduced in length by clockwise rotation. As the valve element 16 temporarily tends to retain its position relative to the cylinder 14, depression of the valve element 15 establishes a communication between the source of pressure oil and the top chamber of the.cylinder.13 via the duct 17, the groove 49, the ports 50, the groove 48, the port 51, the groove 56 and the duct 18. The bottom chamber of the cylinder 13 is put on exhaust via the duct 19, the groove 57, the ports 52` and the open4 chamber 54. Consequently, theoil under pressure entering the top chamber of the cylinder 13 will move piston 12 downwardly, thereby unthrottling the intake pipe 9 until the pressure of the air flowing in the direction of the arrow in pipe 9 will have increased to a Value properly correlated tothe increased quantity of -fuel injected. The increased pressure is .communicated through thepipe'ZS to the chamber 29 and will compress the compressible member 30 pulling rod 3,1 upwardly and turning lever'32 about its fulcrum 33 in clockwise direction, thereby lowering the valve element 16 until the ports 51 and 52 will have been closed again, thereby arresting the actuator 12, 13 in its new position.

Should the temperature of the combustion-air allowing Ythrough the intake pipe 9 increase, it would be necessary to'increase the pressure of the air in order to keep the weight of the air charge `of the cylinders constant. This is effected in the following manner:

When the temperature of the air increases, the thermo- Vstat 38 expands and causes the bell crank 37 to turn anticlockwise as described hereinabove. This will swing lever 32v so as to move piston 16 upwardly causing it to establish`the communication between the portsiSl and the groove 48 and a communication between the ports 52 and the chamber 54. Hence, the piston 12 will be moved downwardly and will so adjust the throttle valve 10 as to further unthrottle the iiow of air. When the pressure prevailing in the stream 38 of air will have reached the required degree, the compressible member 30 will be compressed turning lever 32 in clockwise direction about the fulcrum 33 until the valve element 16 will have been lrestored to the position in which the ports 5.1 and 52 are closed, `thereby arresting the actuator 12, 13. In the new position of the fulcrum 33 the ratio of the lever arms of lever 32 will'have changed somewhat. That is required because the cylinders are now charged with air having a higher temperature and a higher pressure. Therefore, the influence of pressure and temperature on the weight of the air charge will. have changed.

From the above it will be appreciated that the lever 32 constitutes a means which is responsive to both the vacuum` and the temperature prevailing in the intake pipe9." Let it be `now assumed that the motor vehicleclimbing a mountain enters a region of high 4altitude Where'the atmospheric pressure is extremely low. When the driver desirous vof running the engine at full power depresses the accelerator pedal 2 all the way, the actuator piston 12 will move downwardly to thereby opendthe throttle valve 10 entirely. Because of the low atmospheric pressure, however, the pressure of the air charge will be so low that the weight of the air charge 4will be no longer properly correlated to the quantity of fuel injected. Therefore, it is desirable to reduce the fuel quantity. This object is attained in the following manner:

The actuator, after having opened the throttle valve 10 substantially to its extreme position, continues its movement in the tbrottle-valve-opening direction under the control of the vacuum-responsive means 29-31 until the disk 74 will have moved past the Vport 73, thereby establishing communication between the duct 39 and the top space of the cylinder 13 to which oil under pressure is fed through the duct 18 in the manner described hereinabove. As a result, the re-setting device 41-44 will be activated and will reduce the quantity of fuel injected in the manner described hereinabove involving anti-clockwise rotation of the arm 4S, the shaft 24 and the cam 23. The motion of the fuel control element 3, 4 .towards the left with reference to the drawing will be discontinued when the cam 23 will have lifted arm 21 and valve member 15 connected therewith to an extent closing the ports 51 and 52, thereby interrupting the communication of duct 18 with the source of pressure oil.

The control system described oiers the possibility of various adjustments to meet the requirements of abnormal conditions of operation, for instance for the purpose of starting the engine in cold condition. Such an adjustment may be elfected by manipulation of the handle 72 for instance. lf desired, other stationary fulcrums than pin 20 may be rendered adjustable, such as the fulcrum 36. Y

It' desired, the port 73 and the valve element74 controlling same may be constituted by a valve mechanism mounted outside of cylinder k13 and connected with the piston 12 for operation thereby. a

hen the fuel control member 3, 4 assumes its idling position in which the amount of fuel injected is reduced to the minimum required for the idling operation of the engine, the vacuum pressure prevailing in the intake pipe 9, if properly correlated to the idling quantity o ffuel, is so low as to cause the vacuum-responsive means 29- 31 to turn lever 32 to a substantially horizontal position in which angular displacement of bell crank 37 has very little inliuence upon the valve mechanism 15, 16. In other words, the pin 33V is movable substantially in the direction of the slot 34 without displacing the lever 32, when the control valve 15, 16 causes the actuator 12, 13 to keep the throttle 10 substantially closed. This is in keeping with the fact that a changev of the temperature has but a small influence upon the weight of the air charge of the cylinders when such weight is extremely low as it is in the idling operation of the engine.

AWhile the invention has been described in connection with a preferred embodiment thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, ox' adaptations of the invention following, ini-general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as fall within the scope of the invention or the limits of the appended claims.

What I claim is:

l. Control system for an internal combustion engine of the type in which a fuel-air mixture is compressed in each cycle of operation comprising a movable fuel control membergdetermining the quantity of fuel injected per cycle, an actuating member movable by the operator and .connected with s aid fuel control member,` a throttle valve determining `the quantity of air admitted per cycle to the intake pipe of the engine, means responsive to the vacuum prevailing in said intake pipe, an actuator connected with said throttle for the adjustment thereof and controlled jointly by said vacuum-responsive means and 1by said `control member, a re-setting device coordinated to said control member for moving same in a fnelquantity-reducing direction, means controlled by s aid actuator for activating said re-setting device when said actuator, after having opened said throttle valve, continues ,its movement in the throttle-valve-opening direction under control by said vacuum-responsive means owing to excessively low atmospheric pressure resulting in insuiciency of said quantity of air, and resilient means for connecting said actuating member movable by the operator with said movable fuel control member.

2.. Control system for an internal combustion engine of the type in which a fuel-air mixture is compressed in each'cycle of operation comprising a movable fuel control member determining the quantity of fuel injected per cycle, an actuating member movable by the operator and connected with said fuel control member, a throttle valve determining the quantity of air admitted per cycle to the intake pipe of the engine, means responsive to both the vacuum and the temperature prevailing in said intake pipe, an actuator connected with said throttle for the adjustment thereof and controlled jointly by said means and by said control member, a re-setting device co-ordinated to said control member for moving same in a fuel-quantity-reducing direction, means controlled by said actuator `for activating said re-setting device when said actuator, after having opened said throttle valve, continues its movement in the throtle-valve-opening direction under control by said means owing to excessively low atmospheric pressure or excessive temperature resulting in insuiciency' of said quantity of air, and resilient means for connecting said actuating member movable by the operator with said movable fuel control member.

3. Control system as claimed inclaim l in which said resilient means comprise a mechanism including a biased spring for connecting said actuating member movable by the operator with said movable fuel control member.

4. Control system as claimed in claim l in which said resetting device is of the type operable by uid pressure and in which said means controlled by said actuator for actuating said re-setting device includes valve means connected with said actuator for movement thereby and a source of fluid pressure conneotable by said valve means to said re-setting device for activating same.

5. Control system as claimed in claim l in which both said actuator an dsaid re-setting device are of the type operable by fluid pressure, said means controlled by said actuator for activating said re-setting device including a source of pressure and valve means co-ordinated to and operable by said actuator for connecting said source of pressure to said re-setting device.

6. Control system for an internal combustion engine of the type in which a fuel-air mixture is compressed in each cycle of operation comprising a movable fuel control member determining the quantity of fuel injected per cycle, an actuating member movable by the operator and connected with said fuel control member, a throttle valve determining the quantity of air admitted per cycle to the intake pipe of the engine, means responsive to the vacuum prevailing in said intake pipe, a fluid-operable actuator connected with said throttle for the adjustment thereof, a control valve co-ordinated to said fluid-operable actuator for controlling same and including a movable sleeve element provided with ports and a piston element movable in said sleeve element for controlling said ports, said vacuum-responsive means being connected to one of said elements for adjusting same and said control member being cooperatively connected to the other one o f said elements for adjusting same, a re-settng device co-ordinated to said control member for moving same in a fuel-quantity-reducing direction, and means controlled by said actuator for activating said re-setting device when said actuator, after having opened said throttle valve, continues its movement in the throttle-valveopening direction under control by said vacuum-responsive means owing to excessively low atmospheric pressure resulting in insufficiency of said quantity of air.

l 7. Control system as claimed in claim 6 in which said means responsive to the vacuum prevailing in said intake pipe comprises a hollow compressible member and a chamber surrounding same and communicating with said intake pipe, one end of said compressible member being lixed to a Wall of said chamber, said combination further comprising a lever connected with the other end of said compressible member and with one of said elements of said control valve, a movable fulcrum Vfor said lever and means responsive to the temperature prevailing in said intake pipe and connected to said movable fulcrum, whereby said element of said valve is controlledjointly by said vacuum-responsive means and said temperatureresponsive means.

8. Control system as claimed in claim 7 in which said lever has a slot and in which said fulcrum is formed by a pin slidable in said slot, said pin being movable substantially in the direction of said slot without displacing said lever when said control valve causes said actuator to keep said throttle valve closed.

9. Control system for an internal combustion engine of the type in which a fuel-air mixture is compressed in each cycle of operation comprising a movable fuel control member determining the quantity of fuel injected per cycle, an actuating member movable by the operator and connected with said fuel control member, a throttle valve determining the quantity of air admitted per cycle to the intake pipe of the engine, means responsive to the vacuum prevailing in said intake pipe, a fluid-operable actuator connected With said throttle for the adjustment thereof, a control valve for controlling said actuator, means connecting said control valve with said vacuum-responsive means and with said control member for adjustment thereby, a re-setting device co-ordinated to said control member for moving same in a fuel-quantityreducing direction, and means controlled by said actuator for activating said re-setting device when said actuator, after having opened said throttle valve, continues its movement in the throttle-valve-opening direction under control by said vacuum-responsive means owing to excessively low atmospheric pressure resulting in insufficiency of said quantity of air.

10. Control system as claimed in claim 9 in which said re-setting device is of the type operable by fluid pressure, said actuator comprising a cylinder and a piston movable therein, said cylinder being provided with a port so located as to be uncovered and thereby put n communication with said control valve when said actuator, after having opened said throttle valve, continues its movement in the throttle-valve-opening direction, and a duct connecting said port to said re-setting device.

1l. Control system for an internal combustion engine of the type in which a fuel-air mixture is compressed in each cycle of operation comprising a movable fuel control member determining the quantity of fuel injected per cycle,ran actuating member movable by the operator and connected with said fuel control member, a throttle valve determining the quantity of air admitted per cycle to the intake pipe of the engine, means responsive to both the vacuum and the temperature prevailing in said intake pipe, a fluid-operable actuator connected with said throttle for the adjustment thereof, a control valve for controlling said actuator, means connecting said control valve with said means and with said control member for adjustment thereby, a re-setting device coordinated toV said control member for moving same in a cessively 'low atmospheric pressure or excessive temperature resulting in insuciency of said quantity of air. References Cited in the le of this patent UNITED STATES PATENTS Mock Sept. 2, 1947 

